These projects have considered the processing of sound at various stages in the auditory system. These studies include: (1) Theoretical models of the peripheral stages of the system. The computed results agree well with experimental findings and help explain several observed nonlinear phenomena. (2) The development of realistic algorithms (as model neural networks) to process speech evoked activity on the auditory nerve. The results point to new ways of viewing the auditory nerve code. (3) Analysis of data from neurophysiological experiments in the squirrel monkey cortex. The data lend strong support to the existance of a lateral inhibitory-type of processing even at higher auditory centers.